Role of GPI-Anchored CD52 Glycoprotein in Sperm Function

描述（由申请人提供）：CD52是一种局限于男性生殖道和淋巴细胞的gpi锚定糖蛋白。尽管CD52的结构已被广泛表征，淋巴细胞CD52的功能也已被研究，但CD52在精子成熟和功能中的作用尚不清楚。在淋巴细胞表面，CD52与T细胞受体相关，存在于含有酪氨酸激酶活性的蛋白复合物中；含有cd52复合物的交联被证明可以触发蛋白酪氨酸磷酸化并诱导T细胞活化。因此，CD52在与tcr依赖性淋巴细胞激活相关的信号转导事件中被指出。我们假设精子表面CD52具有与淋巴细胞相似的信号转导相关功能和复合物形成特性。在精子中，利用精子CD52特异性单克隆抗体（mAb） S19获得了对CD52功能作用的深入了解。S19 Fab片段被证明可以抑制人类精子与透明带的紧密结合，这暗示了CD52本身或含有CD52的复合物在精子与透明带的相互作用中。初步结果表明，与二价S19单抗孵育的人精子促进顶体反应（AR），而单价S19 Fab则没有。这些结果表明，CD52聚集在精子AR诱导中起作用，AR是一种信号转导介导的事件，发生在精子与透明带结合时。总的来说，精子和淋巴细胞的研究结果暗示了CD52在精子成熟和/或功能中的功能作用。为了验证我们的假设，拟议研究项目的具体目的是研究CD52在人类精子AR中的功能，并鉴定与精子CD52相关的蛋白质。将确定cd52诱导的AR的容能依赖性和钙依赖性。将检查对百日咳毒素抑制的敏感性，以确定观察到的AR是否通过G蛋白介导的途径发生。精子表面CD52交联后蛋白酪氨酸磷酸化的变化将被确定。此外，cd52相关的精子蛋白将被分离并进行微测序。所鉴定的cd52相关蛋白将代表参与精子功能和精子带相互作用的信号转导事件的候选分子。这些研究将为精子CD52的功能和AR的信号转导机制提供深入的见解。

DESCRIPTION (provided by applicant): CD52 is a GPI-anchored glycoprotein restricted to the male reproductive tract and lymphocytes. Although the structure of CD52 has been extensively characterized and the function of lymphocyte CD52 has been investigated, the role of CD52 in sperm maturation and function is unknown. On the lymphocyte surface, CD52 is associated with the T cell receptor and is present in protein complexes containing tyrosine kinase activity; cross linking of CD52-containing complexes were shown to trigger protein tyrosine phosphorylation and induce T cell activation. Thus, CD52 is indicated in signal transduction events associated with TCR-dependent activation of lymphocytes. We hypothesize that sperm-surface CD52 exhibits similar signal transduction-related functions and complex-forming properties as those identified in the lymphocyte. In spermatozoa, insights into the functional role of CD52 have been obtained using S19, a monoclonal antibody (mAb) specific for sperm CD52. S19 Fab fragments were shown to inhibit human sperm-zona pellucida tight binding implicating CD52 itself or a CD52-containing complex in sperm-zona interactions. Preliminary results indicate that incubation of human spermatozoa with the bivalent S19 mAb promotes the acrosome reaction (AR) while monovalent S19 Fab does not. These results suggest that CD52 aggregation has a role in induction of the sperm AR, a signal transduction-mediated event that occurs upon sperm-zona pellucida binding. Collectively, results from sperm and lymphocyte studies implicate a functional role for CD52 in sperm maturation and/or function. To test our hypotheses, the specific aims of the proposed research project are to investigate the function of CD52 in the human sperm AR and to identify proteins associated with sperm CD52. The capacitation- and calcium-dependence of the CD52-induced AR will be determined. Sensitivity to inhibition by pertussis toxin will be examined to determine whether the observed AR occurs via a G protein-mediated pathway. Changes in protein tyrosine phosphorylation upon cross linking of sperm- surface CD52 will be determined. Furthermore, CD52-associated sperm proteins will be isolated and microsequenced. The identified CD52-associated proteins will represent candidate molecules for signal transduction events involved in sperm function and for sperm-zona interactions. These studies will provide insights into the function of sperm CD52 and into the signal transduction mechanisms involved in the AR.